UI Nits: Fix splitter expanding

Since the treeviews didn't fill the space in the sidebar.
This was because the splitter itself wasn't expanding since it
used the sizepolicy of its children.

.. not sure the class hierarchy is right for this stuff, but will
stick with it for now.
UI Nits: Sidebar WIP
Move extra menu
Added Garmin Edge 510
UI Nits: Splitter decor

Moved icon bar back to the bottom and made Splitter handle
same size as scope bar.

The splitter handle paint artefacts were caused by splitter
size restore from before the "new" splitter. We will need to
rename all the settings to ensure we don't get incorrect sizes
for them in future.